candee



Oct. 29, 1929. A. H. CANDEE METHOD OF PRODUCING GEARS 2 Sheets-Sheet 1 Filed Dec. 22, 1926 INVENTOR HZlanH. Candee Fig.2 a

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ATTORNEW Oct. 29, 1929. A. H. CANDEE METHOD OF PRODUCING GEARS 2 Sheets-Sheet 2 Filed D60. 22, 1926 RglZ INVENTOR F114. 13 Allan IiCandee B ATTORNEY% DEE, OF EQOHESTER, NEW YORK, ASSIGNOR TO GLEASON WORKS, OF

ROCHESTER, NEXV YORK, A CORPORATION OF NEVT YORK METHOD OF PRODUCING GEARS Application filed December 22, 1928.

of longitudinally curved tooth tapered gears.

The primary object of the present inven- 5 tion is to provide a method for correctly hoblil bing tapered gears conjugate to a basic crown gear having teeth curved longitudinally along true involutes of a base circle.

A further objectot the present invention is to provide a method whereby a hob of constant pitch of the type commonly used in the hobbing of spur gears may be employed in producing gears conjugate to a bas1c crown gear which is pro ided with longitudinally curved teeth which in the pitch plane are involutes of a base circle.

Another object of the present invention is to provide method of hobbing longitudinalcurved tooth tapered gears, where the basic crown is provided with longitudinally curved teeth which in the pitch plane and in any other plane parallel thereto are of involute curvature lengthwise.

Other objects of the invention will be app rentherein er from the specification and i rom the recital of the appended claims.

The manner of carrying out my invention is illustrated in the accompanying drawings, in which Figure 1 is a diagrammatic view, illustrating' the form ct an involute curve anc its natu" hob of constant pitch, such as is ordinarily eimiloyed in bobbing spur gears, should be positioned to engage the longitudinally cencave tooth sides of a crown gear having teeth of involute lengthwise curvature or to produce bevel gears conjugate to this basic crown gear. This view is a sectional plan view through the hob and crown gear taken in the pitch plane or a plane parallel thereto;

Figure 3 is a diagrammatic view or a spur hob of constant pitch, showing the threat prior to being gashed and relieved, and showing sections through this thread in planes tangent to the pitch and root cylinders and in an ar al plane, respectively;

Figure l is an end view of this hob;

Serial No. 156,387.

Figure 5 is a side elevation of an involute spur hob, two of the thread convolutions being shown prior to being gashed and relieved in sections taken, respectively, in a plane tangent to the base cylinder and in an axial plane of the hob.

Figure 6 is another view of the same hob, showing sections through the thread convolutions, taken, respectively, in planes tangent to the pitch and root cylinders of the hob;

Figure 7 is an end elevation of the hob shown in Figures 5 and 6;

Figure 8 is a view of a tapered involute hob, prior to being gashed and relieved, the upper part being shown in a section in axial plane;

Figure 9 is a sectional view in the pitch plane of a crown gear, showing the hob of Figure 8 in engagement with the crown gear;

Figure 10 is a sectional view through taper hob and crown gear taken in a plane tangent simultaneously to a base cylinder of the hob and the base circle of the crown gear;

Figure 11 is a view similar to Figure 2, illustrating the manner in which a hob or constant pitch and specifically a cylindrical hob, may be positioned in engagement with the convex sides of the teeth of an involute crown gear and employed in producing the convex sides of the teeth or" a bevel gear conjugate to this basic crown gear;

Figures 12 and 13, are a diagrammatic side elevation and plan view, respectively, showing the method of rolling a hob and gear blank together to produce teeth on the blank conjugate to a basic crown gear, of the type illustrated in Figures 2, 9, 10 and 11.

The principal purpose of this invention, as previously stated, is to hob gears conjugate to a basic crown gear having teeth which e2:- tend in involute curves from a base circle.

In describing this invention hereinafter in the specification, reference is made to the production of crown gears. This is done principally because it is much easier to de termine the form and position of hob required for producing a particular bevel gear by analyzing the relationship between the hob and the crown gear which "forms the basis of the system.

(Z at any point a in Le curve crosses ght angles a tangent Z) to the base circi- 0 Iron.

which the curve is derived.

To hob a crown gear, therefore, having teeth which extend in true in'volute curves from a base circle, one basic requirement is that the hob thread when in proper cutting ponition crosses at right angles a line tangentto the base circle of the crown gear.

A series of equi-spaced points on the string 6 will generate similar curves, all of which are parallel to one another. in a crown gear, therefore, having teeth extending in true involute curves trom a base circle, the teeth will be of constant pitch along any line tangent to the base circle oi the crown gear. A second requirement: for hobbing such a gear, therefore, is that the thread of the hob, when in proper cutting posit-ion, be of constant pitch along a line tangent to the base circle of he crown gear.

in Figure 2, a fragmentary sectional view an irivolute crown gear shown. This ngure may also be considered as showing a evel gear produced according to this invenon since in he plane of development the "ructure of a bevel gear and or the crown gear from which it is derived are the same. The whose axis is at 10 has teeth 11 which have surfaces 12 and 13 extending in true involute curves from the base circle 14. The .-*h are or constant pitch along any a line. as the line 15, tangent to the base This line 15 is also a normal or ierpendicular to the tooth curves, already ribed with ref rence to Figure 1. The .rttaces 12 and 13 cross the line 15,

is alread stated, to produce the teeth of the crown rear. the hob must be so positioned relative b01119 crown gear that its threads cross the tangent at angles and this liiie the hob threads must be tant pitch. o such as is commonly used in l10bl3l' is shown in l igures and 1. For pose of clearness, the hob is shown as oear prior to being gushed and This hob of con pitch in e or in any p one parallel thereto. e one convolution 17 of the hob iilliit, taken in a plane tangent to the h surface 18 oil: the hob is shown at 19 in :re 3. This section is on the line pp of .i'fore. ri 'ht angles. 1

re ieved.

Figure In this plane, at the point 20, otlset from the hob axis by a distance f, a tangent 21 to the side 17 01" the hob thread convolution 17 is perpendicular to the hob axis 22. For the opposite sides 17 of the thread convolutions, the points, in this plane, at which the tangents are perpendicular to the hob axis will lie on the opposite side of the axis from the point 20, as indicated at 20.

By placin the hob 16, therefore. as shown in Figure 2, so that its axis 22 is on'set from and parallel to the tangent 15 of the crown gear base circle 14 by an amount equal to the ollset or the points 20 in the sides of the hob thread from the hob axis 22, and imparting to the hob and crown gear the required relae movements, tooth surfaces, in this case the longitudinally concave surfaces will be produced on the crown gear which exteno in the pitch plane of the crown gear in true iuvolute curves from the base circle 14. The hob thread crosses the line 15 at right angles, tan' nts to the points 20 on the sides successive thread convolutions being perpendicular to hob axis 22, and the hob threads are oi constant pitch along said line 15. Gnly one side of the teeth of the crown gear can be cut with exact mathematical accuracy in any one setting 01" this hob, since the points at which the tangents are perpendicular to the hob axis lie on dillerent sides of the axis for opposite sides 01 the thread.

The width of the thread convolutions of the hob, therefore, will be made less than the width oi? the tooth space to be produced on the crown gear and only one side of the hread of the hob will be in finish cutting *ontact with the tooth sides of the crown gear i. any one setting of the hob.

The hob 1G, moreover, can only produce true lIllVOllliG curves in one plane, for any particular setting. For in any plane parallel to the plane 29- as the plane rr, Figure 4;, tangent to the root cylinder 23 of the hob, a point at which a tan 'ent 25 to the side of the hob thread is perpendicular to the hob azris 22 will be oilset from the hob axis by an amount 9 slightly different from the offset 7 of the point 20 from the hob axis. It. then, the hob axis 22 is oliset from the tangent 15 by an amount f equal to the amount of olfset the point 20 from the axis 22, the hob will produce true involute curves in the pitch plane the crown gear. Butif the hob axis is offset from the line 15 by an amount 9 e cal to the offset of the point 2 1- from the s tl e hob will produce true involute curves in the root plane of the crown gear. 'i rue involute curves can be produced in any other plane by ofiisetting the hob axis from the line 15 by the amount of oiiset of the points in that plane, at which the tangents, are perpend cular to the hob axis, but with a hob of the type referred to, at any one setting, true ihvolute curves can be produced in only one plane 43" the crown gear.

With it hob web. as described, in my Pet- 9 4 out ho. 1,111 55,931. above reierreo. to, true 1n- Jo lite on" .-:s ooh be produced on the crown gear 1,

I V V l irohi the hob previousi (.iiiS-Ltlli. 5.5 euttnrgg edges trying 1 lllYUt eiirroeee ltfi thread so e our:

hieh simultaneous;

he hob and IHOV ily. perpeodieiihir to the are t is type, the bed thread extends HO iiivolirte of a base circle 30, 3 end of the bob 1% in a plane ociis extends along an In on axial piano,

thread e hoo bein.

no side 36 ot the hob thread wi ie other sir e 3'? curved. iiie hob, therefore, one h the otrziig the crown gear. in :2

inder 30 on the hob axis 38 the side or o protiie and the side This hob is; of con: .i 'eiie or in any plane perhowever,

d 6 two of the threudcoir vohitione .11 (iii the hob sh. W11 prior to being: geshed end relieved or. d 6f the dread eonvoiutioiis 44; and ab are i, Hi fili'd after the thread hes; been. fl 'itilSd and reiieveo. The eiittin ed es e2 and 13 i" reied i i L "o flushing end relieving, lie in he icoidzii minim-tier: eoiitorinhigr to the Side surfaces 0'; the orieinni thread. is it section through "breed eoiii oiutioii in. a plane f-g) teno the pitch o iiider 49 of the hob. in :1 the ooh 427, et Whirl tangents is: 50 of the hob thread are per- I, ii, 'i i re hob eerie are ofteet troni it 52 equal to Hi) i this ()I' 30 of the hob. on;

Xie 38, Wiii be t A i i 7. i 'e z'ore. the pomte at W of the hob thie hob will produce to faces on he cm 1) gem.- WillCh ere iirointe ieiigthwise curvatur pit h phiie, but in every 1 Lil-Q pi'o eetioii ot ito /1 pie ere-rm gear 15 of? a teligeiy to 1 7 er mm 'er-.1, as w it be more *3 ere; rapidly In curred t ebie i' avoid e nerdy d- V ibiiese circle of t V (me 5 neter of the taper hob i e, .1 7, 1e node eiiieiiei time t out interterei'ie like my cyiindr col 1 3e will orodii e t side feces of the The taper hob, hi:

I hob, has its cutting q invohi LG helieoidai i rty improved term of; taper hob 1S as ior'e mess the hob threads are shown prior to be )1 ,1 p Tm] T- u a 4 51th 1{/C Miler A, 16 1 iii Ullb 1) hi0; rm.

"he sides of the threads of the hob TH E in the axial plane, the sides of the hob threads are of curved profile, as shown in section in Figure 8, but in a plane tangent to base cylinder from which it is derived, side, ndicated at 65, of the hob thread profile, as shown in Figure duce a straight sided profile gear 66. In this plane tangent inder, the opposite sides of the x will be of curved profile. The Mr th of a thread convolution, as with the hobs previously discussed will be less, there- .e, than the width of the tooth space to be produced upon the crown gear and only one e of the thread of the hob will be in finish Contact with the teeth of; the crown in any one setting of the hob. us in the involute cylindrical hob, in the or hob oi the involute type, the points 69 in the corresponding sides of successive thread ,volutions, at which tangents are perpenilar to the hob axis 68, will be offset from lelanes by an amount equal to the radius a base cylinder of the hob and, therefore,

the plane of the crown gear is offset n the line 71 tangent to the base circle 7 2 o L the crown gear, by an amount equal to the radius of a base cylinder of the hob, the hob will produce tooth surfaces on corresponding sides or" the crown gear which are of involute l igthwise curvature in all planes.

7th either the cylindrical or taper hob described, only one side of the teeth of the crown gear can be finish cut in any one setting ot the hob. The opposite sides of the teeth of the crown gear may be produced with a hob of opposite hand positioned on the same side of the base circle tangent of the crown gear and offset from said tangent by amount determined in accordance with the 1 inciples already discussed.

T is possible, however, to employ the same hoe, whether that be cylindrical or tapered, and cut in successive settings, both sides of he teeth of the crown gear. Figure 11 illusrates how this may be accomplished. In .re 2 the longitudinally concave sides of teeth of the crown gear are cut by positioning the hob with its axis 22 offset on one side of the line 15 tangent to the base circle 14- of the crown gear. This. offset is detern ined, as already described, by the amount offset of the points in the sides of successive thread convolutions from the axis 22. The convex sides 12 of the crown gear teeth can be cut with the same hob 16 by positioning its axis 22 in offset relation on the other side of the line 10. The amount of this offset will be determined by the amount of offset from t e hob axis 68 of the points 20 in the side 1'? of the hob thread, which is in finish cutting contact with the convex sides 12 of the crown gear teeth, at which the tangents to successive thread convolutions are perpendicular to the hob axis 22. For the usual spur hob of constant pitch, the amount of this odset will be vleterinined from the particular plane in which it is desired to out true involute curves upon the crown gear. F or the ordinary spur hob of constant pitch the amount of offset of the hob axis 22 from the line 15 on opposite sides of the line 15 will be the same for a given plane. In the involute cylindrical hob, such as illustrated in Figures and (3, in cutting opposite sides of the teeth, the hob axis will be offset equal amounts on opposite sides of the tangent 15, equal to the radius of the base cylinder of the hob. l Vhen the involute taper hob, such as is illustrated in Figures 8, 9 and 10, is employed, the offset of the axis from the line 15 will be different for different sides of the teeth of the crown gear, corresponding to the difference in the size of the base cylinders 61 and 62 from which the opposite sides of the hob threads are derived.

Figures 12 and 13 show, diagrammatically, the manner of moving a hob and tapered gear blank relatively to each other to produce teeth upon the blank conjugate to the basic crown gear described. The hob shown for the purpose as cylindrical, but which, as will be understood, may be tapered or cylindrical and of the usual form or of the involute type, will be positioned relatively to the blank 82 so that its axis 81 is offset by the determined amount, as already described, from and parallel to a line 79 tangent to the base circle 83 of the crown gear. The blank will be so positioned that its axis 84 intersects the axis 85 of he crown gear 86 and the apex of the blank coincides with the apex or center 85 oi the crown gear. The hob and blank are then rotated in engagement about their respective axes and simultaneously a continuous relative movement will be imparted bet veen the hob and blank about the axis 85 or" the crown gear, this movement corresponding to that of a gear meshing with the crown gear. T in this manner, tooth surfaces will be pro duced on one side of the teeth of the blank which are conjugate to tooth surfaces on corresponding sides of the teeth of the crown gear. For cutting the opposite sides of the teeth of the blank, the hob position will be changed or a different hob employed, as described above. An initial position of the hob is shown in Figure 13 in dotted lines at 80'. The hob is translated in the direction indi cated by the arrow 87, while the arrows 8S and 89 indicate the directions of rotation of the hob and blank respectively.

lVhile I have described my invention in connection with the production of bevel gears specifically, it will be understood that it may be applied, also, to the production of other types of gears, particularly to the production of cars from conical blanks as l ln gene 21]., s

gears. while I have illu V and dcsn. ed certain prefered embodmicnts ot my invention, it will be underctood that the invention is capable of turt 161 modificationsand adaptations within the limits ii. the disclosure and the scope of the appndei claims and that iii; applica'ci is intende c to cove' any variations, uses or adaptatiom oi my inventiiin, following, in general, tlu priuc'ples ot the invention and inchuling such departures from the pres-nt disclosure as may come within known or customary practice in the gear art and may be applied to the essential ioatures hereinbett'ore set forth and as "fall within the limits of the appended claims.

llavin thus described my invention, what I claim is:

1. The method of cu ting the side faces of the teeth of a tapered gear having: longitudinally curved teeth, which in development are of constant pitch along a straight line oli'set from the axis, which consists in positioning a hob which. is of constant pitch in an axial plane relatively to the blank so that the projection of the axis of the hob into the plane of development is otlset from and parallel to said line of constant pitch and so that the hob thread convolntions have the same direction at said line of constant pitch as have the teeth of the gear to be cut and rotating; the hob in llllQl'HlQSlllIlQ engagement with the blank while rotating the blank continuously on its 2. The method of cutting the side faces of the teeth of a tapered having longitudinally curved teeth, which in development are olt constant pitch along a straight line oil'so from its axis,v which consists in positioning a hob which of constant pitch in an axial plane relative to the blank so that the projection of the a 'is ol: the hob into the plane or? devcioptnem, .i i'roin and par allel to said line o1 constant pitch and so that the hob thread convolutions have the same direction said line 01%. constant pitch as have the teeth of the gear to be cut and rotating: said hob in. intermeshing engagement with the blank while 'otating the blank continuously on its axis and simultaneously producing a continuous relative rolling movement between the hob and blank.

3. The method oi? cutting the side faces of the teeth ot a gear conjugate to a basic crown. ,e'ecr having longitudinally curved teeth which are of constant pitch along a straight line ollset from its axis, which consists in selecting: a nob of constant pitch and ning the hob so that the projection of into the plane of the crown gear is offset from and parallel to said line of constant pitch of the crown gear and that the thread convolutions of the hob have the same direction at said line of constant pitch as have the teeth of the crown gear, at d rotatsaid hob in continuous intermeshing on .inent with the blank while rotating the continuously on its axis and simultal blank ncously imparting a continuous relative roll Ill," movement between the hob and blank corres )llillzlg to that ot a gear meshing; with the rown gear.

4:. The method of cuttin J the teeth of a tapered jear ha a dii ally curveil teeth which dovclo "1 are of constant pitch along a straie'l otl'sct fr nn its axis, which consirts in p 9' the side vi lei r tioning hob having threads or cor r pitch relatively to the gear blank so that, n

L I J 4 l or tile development, the point 1n.

the of the successive thread convo plane the sides 1 tions at which the tangents are perpendnarar to the hob axis, lie on said line of COllSLfillil pitch, and rotatim said hob in int rahmg;- engagrement wi the gear blan while pitch rel :tively to the gem. blanl: so that, ii. he 1e of the development, the points in he .es ot successive tnread convolutions it vl i 'h the tangents are perpendicular to the iob axis, he on said line of constant pitch and rotating said hob in intermeslnng engagement with the blank while rotating the blank continuously on its axis and simultz neously producing a continuous rela 0 rolling movement between the hob and blank.

6. The method of Cli'il "he side 'acim oi" the eeth of a gear conjuga I 3 gear having longitudina which are of constant p" line offset from its a selecting a hob, havi i pitch, and positioninp' blank so 1 l at the po c ssive thread convol tangents are perpeudicuh lie on said lii e oi constan ing said hob 11 co tinuous into gagxment with th blank continuously on axis 331i. ously imparting the conti anon ing movement between the h a manner of a gear mesh 7. The niiethod of cutting r i. the teeth of a gear conjugate to gear whose teeth extend in ol re-m a base circle, which consist blank whi e from w iich the longitudinal curvature of the crown gear teeth are derived, and rotating the hob in intermeshin engagement with the blank while rotating the blank continuously on its axis and iultaneously imparting a continuous relative rolling movement between the hob and blank corres onding to that of a meshing with the crown gear.

b. The method of cutting the side laces oi the teeth of a longitudinally curved tooth tapered gear which in development is or con stant pitch along a straight line otl'set fr .;n its axis, which consists in positioning; a hob of constant pitch relatively to the gear blank so that, in the plane of the development, the axis of the hob is offset from and parallel to said line of constant pitch and so that points in the sides of successive thread convolutions, at which tangents are perpendicular to the hob axis, lie on said line of constant pitch and rotating the hob in intermeshing engagement with the blank while rotating the blank continuously on its axis.

9. The method of cutting the side faces of the teeth of a longitudinally curved tooth tapered gear which in development is oiconstant pitch along a straight line offset from the axis, which consists in positioning a hob of constant pitch relative to the gear blank so that the projection of the hob axis in the plane of the developmentis offsetfrom and parallel to said line of constant pitch and that the points in the sides of successive thread convolutions at which the tangents are perpendicular to the hob axis, lie on said line of constant pitch, and rotating the hob in intermeshing engagement with the blank while rotating the blank continuously on its axis and simultaneously producing a continuous relative rolling movement between the hob and blank.

10. The method of cutting the side faces of the teeth of a gear which is conjugate to a basic crown gear having longitudinally curved teeth which are of constant pitch along a straight line offset from the axis, which consists in positioning a hob of con stant pitch relative to the gear blank so that the projection of the hob axis into the plane of the crown gear is offset from and parallel to said line of constant pitch of the crown gear and that the points in the sides of successive thread convolutions, at which the tangents are perpendicular to the hob axis, lie on said line of constant pitch and rotating the hob in continuous intermeshing engagement with the blank while rotating the blank continuously on its axis and simultaneously imparting a continuous relative rolling movement between the hob and blank corresponding to that of a gear meshing with the crown gear.

11. The method of cutting the side faces of the teeth of a gear conjugate to a basic crown gear having teeth extending in involute curves from a base circle which consists in positioning a hob of constant pi ch relative to a gear blank so that the projection of the hob axis into the plane of the gear is offset from and para tangent to said base circle and th: in the sides ot the successive tl lutions, at which the tangents dicular to the hob axis, lie on to the base circle, and rotating inter-meshing engagement with while rotating the blank continue sly on it axis and simultaneously producing a continuous relative rolling movement between the hob and blank corresponding to that of a gear meshing with the crown 12. tie s-de of the teeth of a longitudina curved tootn tapered gear which evelopment of or stant pitch along a straight line ottset trol '1 the axis which consists in positi a taper hob of constant pitch in an axial plane relative to the gear blank so that the projection of the hob axis in the plane of the development is offset from and parallel to said line of constant pitch and that the thread convolutions of the hob hare the same direction at said line of constant pitch have the teeth of the gear to be cut and rotating said hob in intermeshing engagement with the blank while rotating the blank continuously on its axis.

13. The method of cutting the side of the teeth of longitudinally curved tapered gear which in development constant pitch along a straight line C TO 'Wll The method of cutt offset from its axis which consists in positioning a taper hob of constant pitch in an axial plane relative to the gear blank, so that the, projection of the hob axis into the plane of the development is offset from and parallel to said line of cons fit pitch and no that the thread convolutions of the hob have the same direction at said line or constant pitch as have the teeth 0:? the ar to be cut, and retating said hob in intcrmeshing engagement with the gear blank while rotating the blank continuously on its axis and simultaneously producing a continuous relative rellin movementbetween the hob and blank.

1 t. The method cutting the side faces of the teeth ot a longitudinally curved tooth ll euiti e to a n u onion so that .heprojec Cu sinto the ploneoi the dcvflopincnt set v roi'n and p orullel to sand line of c u t h and so that the SUCCGSSLTG threzid conut which the tuu uts ure oerpenpoints in voluti ens c.

1 1 id line of mb in indiculnr to the hot; 1, iii? on blank l l! the sides C;

t 1011" with the gear constunt pitch, :1: l at termeshiug chos -en l while rotating;- the hill: continuously on "ts axis uud sunul 8.714) importing; con

1, i tinuous relative rolling motion between the hob and blank.

16. The method of cu Q .1@ side i eces 1' a rear conjugate to u basic crown g ean hr.

eoth extending in inyoh' mse circle, which con uper hob oi constant p 1 1h! oh so that the project nto the plane of the crown gear end nu'nllel to a line tangent to s circle and that the poi eessivc thread eons. tangents ere PQ'LPQDLKJHlRl to i on said tungent to the hav '3. so 'd hob iu intern'ieshin geer blunh While rote. eusly on its unis and 5 inc; :1 continuous rci: between the hob enl ll'l' thot .t u 11lllGSlllllgZ'Witll 17 The method of ch of a. longitudinally curred which consists in POFlilzlilliW its cutting edges lying in coidul surface, with its axis o 1 axis of the blank to be cut out said hob in continuous iutcrinesl nieut with the rear blank While blank eontiruumsly on its unis.

18. The method I n loug itudinelly curved which cons "sitio l L t I. L i

With the continu- )L'OflllC- elneut responding to e crm *u go the side .1 tuueren {your hob huviu involulc lichset from h l in rote its cutting: 1155 in in o hoi; suritzicesu with J e'lli'set tron :h u:

and. the rom: blunt: coutinuousl .xterrueshint; {EHQEUIQEL unnorti '2. continuous 1 inoren'ient between the 1 the blank to he cut and in rotating s:

v on their While siinu. relative rolling); and blank.

19. The method of do feces (it :i. long ituc f .elly cur -red tooth tupereu gear wh ch consists in positioning); u hob. hori if ,ts cutting; edges iyiu in involutc heli coildul surfeces ith its axis offset from the unis 0t tlo gear blank to be cut and in rotstinp; id hob and blank continuously on their respecau'ltino; the

hing engagement, iyhile rtzne" :1 relative roll ng 121': hob and blank corre- .s i s eer meshing; with :i

of the development is offset from the 7 plane said hue oi sq mi LO tle radius of the 156 cylinder oi: the hob and reunio sold hob 1n iuterineshi ment with the e; blunt: While -r w a) Jiflllil continuously on H -g A 1",; .1. cow 1 tie and been 'lStilCKl oil? 0 faces ()1 a. gear \vhich 1s con ugnte to u Josie crown W1 1 d in inyelu'e rose teeth ezitru b circle, WlllCil. consists 1n hav ng; its cutting edges ielicoioul surieces, relative so that the PI'OJQCtlOll of and lototing said hob in continuous intereu 'egcinent with the blank While rotating the blank continuously on its s end sinullteneously producing a cortiuuous relative rolling movement between oh and blank corresponding to that of ieshiug with the crown gear.

The method of cutting the side tooth oi? u longitudinally curved tooth tuwhich in development is of onpitch along a straight line offset from faces of a. gear which is conjugate to :1 basic crown r Whose teeth extend in inyolute curves ii roi a base circle which consists in positioning; a taper hob, having its cutting edges lying in involute helicoidel surfaces, relative to the gear blank so that a plane tuu z'ent to the base cylinder oi? the hob end paralle to the axis of the crown passes through said line of constant pitch and rotut- I said hob in intermeshing engagement with the gear blank While rotating the blank continuously on its axis and simultaneously producing a continuous relative rolling inoyement between the hob and blank corresponding to that of agear meshing with a crown gear.

24. The method of cutting a longitudinally curved tooth tapered gear which in development is of constant pitch along a straight line ollfset from its axis which consists in cutting corresponding sides of all the teeth of the blank with a hob of constant pitch, so positioned relative to the blank that the projection of its axis into the plane of the development is oiiset to one side of the line of constant pitch, and cutting the opposite sides of the teeth of the blank with the same hob so positioned that its axis is offset on the other side of the line of constant pitch, the hob being rotated, during each cutting operation, in continuous intermesliing engagement with the blank while the blank is rotated continuously on its axis.

25. The method of cutting a gear conju gate to a crown gear whose teeth extend in involute curves from a base circle, which consists in cutting corresponding sides of all the teeth of the blank with a hob of constant pitch so positioned relative to the blank that the projection of its axis into the plane of the crown gear is offset to one side of a line tangent to said base circle, and cutting the opposite sides of the teeth of the blank with the same hob so positioned that the projection of its axis is offset to the other side of the tangent to said base circle, the hob being rotated during each cutting operation in continuous intermeshing engagement with the gear blank while the blank is rotated continuously on its axis and a continuous relative rolling movement is simultaneously imparted between the hob and blank corresponding to that of a gear meshing with the crown gear.

26. The method of cutting a longitudinally curved tooth tapered gear which is of constant pitch in development along a straight line o'llset from the axis, which consists in cutting corresponding sides of all the teeth of the blank with a hob of constant pitch so positioned relative to the blank that the projection of its axis into the plane of the development is offset from and parallel to said line of constant pitch and that the points in the sides of successive thread convolutions, at which the tangents are perpendicular to the hob axis, lie on said line of constant pitch, and cutting the opposite sides of the teeth of the blank with the same hob so positioned that the projection of its axis is offset from the opposite side of said line of constant pitch and that the points on the sides of successive thread convolutions, at which the tangents are perpendicular to the hob axis, lie on said line of constant pitch, the hob being rotated, during each cutting operation, in intermeshing engagement with the gear blank while the blank is rotated continuously on its axis.

27. The method of cutting a gear conjugate to a crown. gear having teeth extending" in involute curves from a base circle, which .ts in cutting corresponding sides of all 2 teeth oi the lank with a hob of constant pitch, so positioned that the projection of its into the plane of the crown gear is offrom and parallel to a tangent to said base circle and that the points in the sides of successive thread convolutions, at which the tangents are perpendicular to the hob axis, lie on said tangent to the base circle of the crown gear, and cutting the opposite sides of the teeth of the blank with the same hob so positioned that the projection of its axis is offset on the opposite side of the tangent to the base circle and that the points in the sides of successive thread convolutions, at which the tangents are perpendicular to the hob axis, lie on said line tangent to the base cir- 012, the hob being rotated, during each cuttin operation, in intermeshing engagement ith the blank while the blank is rotated continuously on its axis and while simultaneously a continuous relative rolling movement is imparted between the hob and blank corresponding to that of a gear meshk} with the crown gear. L8. The method of cutting a longitudinally curved tooth tapered gear which is of constant pitch in development along a straight line offset from its axis, which consists in cutting corresponding sides of all the teeth of the blank with a taper hob of constant plane so positioned relative to the blank that the projection of its axis in the pitch of the development is ofi set from and parallel to said line of constant pitch and that the points in the sides of successive thread convolutions, at which the tangents are perpendicular to the hob axis, lie on said line of constant pitch, and cutting the opposite sides of the teeth of the blank with the same hob so positioned that the projection of its axis is offset from the opposite side of said line or" constant pitch and the points in the sides of successive thread convolutions, at which the tangents are perpendicular to the hob axis, lie on said line of constant pitch, the hob being rotated, during each cutting operation, in intermeshing engagement with the gear blank while the blank is continuously rotated on its axis.

29. The method of cutting a gear conjugate to a crown gear having teeth extending in involute curves from a base circle, which consists in cutting corresponding sides of all the teeth of theblank with a taper hob of c011- stant pitch, so positioned relative to the blank that the projection of the hob axis into the plane of the crown gear is oflset from and parallel to a tangent to the base circle of the crown gear and that the points in the sides of successive thread convolutions, at which the tangents are perpendicular to the hob axis, lie on said tangent to the base circle of the crown gear, and cutting the opposite sides of the teeth of the blank with the same hob so positioned that the projection of its axis is oiiset on the opposite side of the tangent to the base circle and that the points in the sides of successive thread convolutions, at which the tangents are perpendicular to the hob axis, lie on said tangent to the base circle, the hob being rotated, during each cutting operation, in intermeshing engagement with the gear blank while the blank is rotated continuously on its axis and while simultaneously a continuous relative rolling movement is imparted between the hob and blank corresponding to that of a gear meshing with the crown gear.

30. The method of cutting a longitudinally curved tooth tapered gear which in development is of constant pitch along a straight line offset from its axis, which consists in cutting corresponding sides of all the teeth of the blank with a hob, having its cutting edges lying in involute helicoidal surfaces, so positioned relative to the gear blank that one side of the hob thread is in finish cutting contact with one side of the teeth of the and that the projection of the hob axis in the plane of the development is offset from said line of constant pitch, by an amount equal to the radius of the base cylinder of the hob, and' cutting the opposite sides of the teeth of the blank with the same hob so positioned that the opposite side of its thread is in finish cutting contact with the other side of the teeth of the blank and with the projection of its axis offset on the opposite side of said line of constant pitch by an amount equal to the radius of its base cylinder, the hob being rotated. during each cutting operation, in continuous engagement with the blank while the blank is rotated continuously on its axis.

31. The method of cutting a gear conjug to a basic crown gear whose teeth extend involute curves from a base circle, which consists in cutting corresponding sides of all the teeth of the blank with a hob, having its cutting edges lying in involute helicoidal surfaces, so positioned. relative to the gear blank that one side of its thread is in finish cuttin ,9; contact with one side of the teeth of the gear and that a plane tangent to the base cylinder of the hob on one side of its axis and parallel to the axis. of the crown 2r pas cs through a tangent to the base c. cle of the crown gear, and cutting the opposite sides of the teeth of the blank with the same hob so positioned that the opposite side of its thread is in finish cutting contact with the other side or the teeth of the blank and that a plane tangent to the base cylinder of the hob on the opposite side of the hob axis and parallel to the axis of the crown gear passes through the tangent to the base circle of the crown gear,

the hob being rotatec, during each cutting operation, in intcrineshing with the blank while the blank is rotatco continuously on its and while simultaneously a continuous relative rolling movement is iinpartet between the hob and blank corresir-ponding to that ot a gear meshing with a crown gear.

The method oi? cutting a longitudinally curved tooth tapered gear which in develop ment is of constant pitch along a straight line offset from its axis which cons. in cutting corresponding sides of all the teeth of the blank with a taper hob, having its cutting edges lying in involute helicoidal surfaces, so positioned relative to the gear blank that one side of its thread is in finish cutting contact with one side of the teeth of the blank and that a plane tangent to the base cvlindcr from which this side of the hob thread is derived passes through the line of constant pitch, and cutting the opposite sides of the teeth of the blank with the same hob so positioned that the opposite side of its thread is in linish cutting contact with the other sides of the teeth of the blank and that a plane tangent to the base cylinder from which the last names side of the hob thread is derived passes through a line of constant pitch of the gear in development, the hob being rotated during each cutting operation, in intermeshing engagement with the gear blank while the blank is rotated continuously on its axis.

33. The method of cutting a gear conjunate to basic crown gear whose teeth extend in involute curves from a base circle, which consists in cutting corresponding sides oi" all the teeth of the blank with a taper hob, having its cutting edges lying in involute helicoidal surfaces, so positioned relative to the gear blank that one side of the thread is in finish cutting contact with one side of the teeth of the gear blank and that a plane parallel to the axis of the crown gear and tangent to the base cylinder from which this side of the hob thread is derived passes through a li re tangent to the base circle of the crown gear, and cutting th opposite sides of the teeth of the blank with the same hob so positioned that the opposite side of its thread is' in finish cutting contact with the other side of the teeth of the gear and that a plane parallel to the axis of the crown gear and tangent to the base cylinder from which the last named side of the hob thread is derived passes through a tangent to the base circle of the crown gear, the hob being rotated, during each cutting operation, in interineshing ens gageinent with the blank while the blank is rotated continuously on its axis and while simultaneously a continuous relative rolling movement is imparted between the hob and blank corresponding to that of a gear meshing with the crown gear.

341. The method of cutting the side faces of the teeth of a longitudinally curved tooth gear which in development is of constant pitch along a straight line offset from its axis, Which consists in positioning a hob relative to a gear blank so that in a plane perpendicular to the plane of the development and passing through said line of constant pitch, the hob thread is also of constant pitch and so that the tangents to the sides of successive thread convolutions at the points of intersection of said thread convolutions with said line are perpendicular to said line, and rotating said hob in intermeshing engagement with the gear blank while rotating the blank continuously on its axis.

35. The method of cutting the side faces of the teeth of a gear conjugate to a basic crown gear having teeth extending in in-- volute curves from a base circle, which consists in positioning a hob relative to the gear blank so that in a plane parallel to the crown gear axis and passing through a line tangent to said base circle, the hob is also of constant pitch and so that the tangents to the sides of successive thread convolutions at the points of intersection of said thread convolutions with said tangent line are perpendicular to said line, and rotating the hob in interrneshing engagement with the gear blank while rotating the blank continuously on its axis and simultaneously producing a relative rolling movement between the hob and blank corresponding to that of a gear meshing with the crown gear.

ALLAN H. CANDEE. 

